國立臺灣大學哲學論評

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This article is concerned with the problem of how to avoid the Third Man Argument which Plato put forward in Parmenides. According to Gregory Vlastos, this argument is based on two tacit assumptions: the Self-Predication and the Non-Identity Assumption. In recent years there have been a number of interpretations which attempted to avoid the Third Man Argument by proving that the Self-Predication Assumption is not an acceptable part of Plato’s theory. However, in this article I will show that the fallacy of the Third Man Argument does not lie in the Self-Predication Assumption, but in the Non-Identity Assumption. That is, we may avoid the Third Man Argument by proving that the Non-Identity Assumption is false.
Moreover, in this article I will point out that by putting forward the Third Man Argument, Plato does not really intend to raise a criticism of his own theory. Rather, the two versions of the Third Man Argument, which are set out in Parmenides 132a1-b2 and 132d1-133a7 respectively, should be considered as his warnings against the possible misunderstandings concerning the relationship between Forms and particulars, i.e. the relationship of “participation.” In other words, if we mistakenly interpret the conception of participation in a materialistic manner, the Theory of Forms will inevitably be caught in the “Largeness Regress”; and if we comprehend the relationship of participation in terms of the “likeness” between Forms and particulars, and consider the later to be a symmetrical relation, then the Theory of Forms must fall into the “Likeness Regress.”